An organic electroluminescence element (organic EL element) is a thin-type complete solid element utilizing electroluminescence produced by an organic material (hereafter, the term “electroluminescence” is also simply called as “EL”) and enabling to emit light at a voltage of approximately a few to a few tens volts. It has excellent features of high luminance, high emission efficiency, thin-type, and lightweight. Therefore, particularly in recent years, an organic EL element using a resin substrate provided with a thin and lightweight gas barrier layer attracts attention as a surface-emitting body used for a backlight in various displays, a display panel of sign or emergency light, or an illuminating light source.
As a resin substrate for a flexible organic EL element, for example, a gas barrier substrate utilizing a polysilazane reforming layer is disclosed (for example, refer to JP-A No. 2014-109001). The present inventors have tried to produce an organic EL element having a thick gas barrier layer. It was found that the produced organic EL element generated cracks when it was bent, and its gas barrier ability was seriously deteriorated.
It was disclosed a gas barrier substrate composed of a functional layer of a thickness of 1 μm to 30 μm sandwiched between two gas barrier layers (for example, refer to WO 2004/101276). The present inventors have tried to produce an organic EL element using a gas barrier substrate composed of a functional layer between two gas barrier layers. It was found that high gas barrier ability can be obtained even when it was bent, however, it was found that high gas barrier ability was insufficient in a durability test under an accelerated condition by using a heat cycle. An example of a heat cycle is as follows: to keep the sample at 85° C. and 85% RH for 120 minutes; to decrease the temperature to −40° C. over a period of 90 minutes and to keep at −40° C. for 120 minutes; and to increase the temperature to 85° C. (with humidity of 85% RH) over a period of 90 minutes and to keep at 85° C. for 80 minutes. A durability test was done by repeating 100 times of the above-described heat cycle processes. It was also found that its stress relief function was insufficient and a gas barrier property after impact test under high temperature and high humidity conditions was considerably deteriorated.